From 939f6e1cd4fadc8d43cd9c5239d36c05cd135f85 Mon Sep 17 00:00:00 2001
From: Marco Gorelli <33491632+MarcoGorelli@users.noreply.github.com>
Date: Wed, 8 Jan 2025 16:56:38 +0000
Subject: [PATCH 1/2] feat: semi join in duckdb

---
 narwhals/_duckdb/dataframe.py | 17 ++++++++++-------
 tests/frame/join_test.py      |  3 ---
 2 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/narwhals/_duckdb/dataframe.py b/narwhals/_duckdb/dataframe.py
index 76ff68ae0..50ea79bdf 100644
--- a/narwhals/_duckdb/dataframe.py
+++ b/narwhals/_duckdb/dataframe.py
@@ -225,7 +225,7 @@ def join(
         if isinstance(right_on, str):
             right_on = [right_on]
 
-        if how not in ("inner", "left"):
+        if how not in ("inner", "left", "semi"):
             msg = "Only inner and left join is implemented for DuckDB"
             raise NotImplementedError(msg)
 
@@ -242,12 +242,15 @@ def join(
             other._native_frame.set_alias("rhs"), condition=condition, how=how
         )
 
-        select = [f"lhs.{x}" for x in self._native_frame.columns]
-        for col in other._native_frame.columns:
-            if col in self._native_frame.columns and col not in right_on:
-                select.append(f"rhs.{col} as {col}{suffix}")
-            elif col not in right_on:
-                select.append(col)
+        if how in ("inner", "left"):
+            select = [f"lhs.{x}" for x in self._native_frame.columns]
+            for col in other._native_frame.columns:
+                if col in self._native_frame.columns and col not in right_on:
+                    select.append(f"rhs.{col} as {col}{suffix}")
+                elif col not in right_on:
+                    select.append(col)
+        elif how == "semi":
+            select = [f"lhs.{x}" for x in self._native_frame.columns]
 
         res = rel.select(", ".join(select)).set_alias(original_alias)
         return self._from_native_frame(res)
diff --git a/tests/frame/join_test.py b/tests/frame/join_test.py
index 7332cb254..242696394 100644
--- a/tests/frame/join_test.py
+++ b/tests/frame/join_test.py
@@ -206,10 +206,7 @@ def test_semi_join(
     join_key: list[str],
     filter_expr: nw.Expr,
     expected: dict[str, list[Any]],
-    request: pytest.FixtureRequest,
 ) -> None:
-    if "duckdb" in str(constructor):
-        request.applymarker(pytest.mark.xfail)
     data = {"antananarivo": [1, 3, 2], "bob": [4, 4, 6], "zorro": [7.0, 8, 9]}
     df = nw.from_native(constructor(data))
     other = df.filter(filter_expr)

From 9d6d370793a58a6f4a0c6c4338ecef848a06ab55 Mon Sep 17 00:00:00 2001
From: Marco Gorelli <33491632+MarcoGorelli@users.noreply.github.com>
Date: Wed, 8 Jan 2025 16:59:06 +0000
Subject: [PATCH 2/2] fixup

---
 tpch/execute.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tpch/execute.py b/tpch/execute.py
index 1f3823ced..427c8cf5b 100644
--- a/tpch/execute.py
+++ b/tpch/execute.py
@@ -40,7 +40,7 @@
     "dask": lambda x: x.compute(),
 }
 
-DUCKDB_XFAILS = ["q11", "q14", "q15", "q16", "q18", "q22"]
+DUCKDB_XFAILS = ["q11", "q14", "q15", "q16", "q22"]
 
 QUERY_DATA_PATH_MAP = {
     "q1": (LINEITEM_PATH,),